The present disclosure relates to a battery cell, preferably a lithium ion battery cell, having a temperature sensor that is arranged in the battery cell housing.
It is apparent that in future both in stationary applications and also in vehicles such as hybrid vehicles and electric vehicles that battery systems will be used on an ever increasing scale. In particular, increasing use will be made of batteries as traction batteries for use in hybrid vehicles and electric vehicles and thus supplying energy to electric drives. FIG. 1 illustrates a battery 200 of this type of the prior art. Said battery comprises a housing 70 and a cell core that comprises an electrode arrangement 10 for generating energy. Mathematical battery models are used for the purpose of operating the battery 200. However, internal resistances and time constants of the dynamic battery cell behavior under load greatly depend upon the temperature in the cell core in which the chemical reactions occur. The temperature in the cell core can change rapidly as a result of the heat that is produced under load. FIG. 2 illustrates by way of example the instantaneous portion of the internal resistance of a 20 Ah battery cell plotted against the temperature. As is evident, the internal resistance undergoes high rates of change particularly in the low temperature range. An incorrectly measured temperature consequently has great influence on the battery states that are determined therefrom and also on the working capacity of the battery that is predicted from said measured temperature.
According to the prior art, the temperature is measured at the battery cells by means of temperature sensors that are attached to the housing. DE 199 61 311 A1 thus discloses a temperature sensor that is fastened to the battery from the outside by means of a battery clamp. The temperature-dependent battery model parameters are then mapped offline or online onto the housing temperature. However, the housing outer temperature corresponds neither to the core temperature inside the housing on the electrode arrangement nor is said housing outer temperature unambiguously associated with said core temperature. Consequently, the measurement of a change of core temperature on the battery cell housing owing to thermal transition resistances inside the cell and towards the outside is delayed or said change is not measured at all.
The inaccurate measurement of the prevailing temperature in the cell core consequently leads to inaccuracies in the temperature-dependent battery models of the operating state of the battery. The battery models can be used both in the battery control device for monitoring and controlling the operation of the battery and also outside the battery in an offline simulation.
DE 100 56 972 A1 discloses a battery cell, wherein sensors are arranged in the housing of a battery cell for the purpose of ascertaining the battery temperature. The temperature sensors are embodied as temperature detectors and are connected to the outer region of the battery housing by way of electrical lines. Although it is possible to ascertain the temperature of the cell core by means of installing conventional sensing elements inside the battery cell, said conventional sensing elements containing for example an NTC measuring unit that has a conventional three dimensional structure, the heat development and the influences of heat in the battery are however influenced by the sensing units and evaluating units and the signal lines.
Moreover, Makinwa and Snoeij (“A CMOS Temperature-to-Frequency Converter With an Inaccuracy of Less Than +−0.5° C. (3σ) from −40° C. to 105° C.”, K. A. A. Makinwa, Martijn F. Snoeij, IEEE Journal of Solid-State Circuits, Vol. 41, No. 12, December 2006, p. 2992-2997) disclose a temperature-to-frequency converter that is implemented in a standard CMOS method.